1. Field of the Invention
The present invention relates to a roller-type straightening apparatus for correcting warping, bending and out-of-squareness of shaped beams, especially H-beams.
2. Description of the Prior Art
In general, rolled H-beams are manufactured by hot rolling by using a universal mill including pairs of web rolls, which are usually generally vertically disposed rolls having their axes in the same generally horizontal plane, sometimes called "horizontal rolls," working in cooperation with right and left flange rolls, generally rotating about vertical axes and sometimes called "vertical rolls."
When an H-beam is cooled after it has been hot rolled, warping, bending and out-of-squareness tend to take place during the cooling process. These defects are usually corrected by using a roller-type straightening apparatus.
The current practice may be understood by referring to FIG. 11 of the drawings, showing a conventional apparatus which performs the correction operation in such a manner that the web 1a of an H-beam 1 is pressed by horizontal rolls 2 disposed vertically alternately in the direction in which the H-beam 1 moves. Acting through the web 1a, they apply bending deformation to flanges 1b. Such bending deformation is repeatedly applied to the flanges 1b during movement of the H-beam 1.
The rolls are arranged in such a manner that the horizontal roll 2 presses the juncture between the web 1a and the flanges 1b to the degree needed to prevent deflection of the web 1a. However, if the pressing load generated is too large, the web 1a is deflected, causing the flange adjacent to the horizontal roll 2 to be inclined inward and to contact the side surface of the horizontal roll 2, causing plastic deformation of the flange. Therefore the desired squareness cannot be realized, producing the type of structure shown in FIG. 12(a) after the attempted correction operation has been completed.
When the pressing load is too large in comparison to the rigidity of the web, deformation takes place in the junction between the web and the flange as shown in FIG. 12(b), and the web can be bent. Therefore, satisfactory correction for warping, bending and out-of-squareness cannot be obtained.
In order to overcome the above-described problems, various devices have been proposed, as disclosed in Japanese Patent Laid-Open No. 56-30027, Japanese Patent Laid-Open No. 56-119624, Japanese Patent Laid-Open No. 57-137028 and the like.
The structure disclosed in Japanese Patent Laid-Open No. 56-30027 is arranged in such a manner that a pair of horizontal rolls and another pair of vertical rolls are disposed in front of or in the rear of the roller-type straightening apparatus. The structure disclosed in Japanese Patent Laid-Open No. 56-119624 is arranged in such a manner that right and left forming rolls are disposed at intervals corresponding to at least three horizontal rolls. Furthermore, the structure disclosed in Japanese Patent Laid-Open No. 57-137028 is arranged in such a manner that each correction roll has a tapered portion on the side surface thereof so as to prevent inclination of the flanges.
However, both the above-described structures disclosed in Japanese Patent Laid-Open Nos. 56-30027 and 56-119624 are arranged in such a manner that each flange of the H-beam is without support at the location of the horizontal roll. Therefore, the flange can be inclined by the pressure of the correcting load, causing the shape of the H-beam to become defective in the ways shown in FIGS. 12(a) and 12(b). Furthermore, the unwanted flange inclination cannot satisfactorily be modified even if the outer surface of the flange is supported by a vertical roll at a position in front of or behind the roller-type straightening apparatus or in a position between the correcting rolls.
Furthermore, the structure disclosed in Japanese Patent Laid-Open No. 57-137028 is arranged in such a manner that the taper given to the side surface of the horizontal roll presses the flange of the H-beam in an inverse direction and causes it to be inclined by the pressing load generated. Therefore, the fear of generation of a defective shape as shown in FIG. 12(a) cannot be eliminated. What is even worse, flaws can be generated in the inner surface of the flange.
A so-called thin-wall H-beam may be designed with a ratio of flange thickness to web thickness which is quite considerable. Its purpose is to improve the quality of rolled H-beams as construction materials. In such a case warping cannot be easily corrected due to the problems already described. On the other hand, since out-of-squareness of the flange cannot be corrected on-line, it must be corrected by separate pressing or heating, relying upon the personal perceptions of workers. This causes serious problems in operational conditions, in manufacturing yield and in quality of product.
Furthermore, when using a conventional center type roll shaft, the roll shaft has to be removed from the roll chock bearing to exchange the horizontal rolls which are fastened via sleeves and the like. Therefore, excessive labor and time are required, increasing manufacturing cost.